The present invention relates to a leveling device for use in measuring the direction of illumination in the lateral direction of a vehicular headlamp to allow a determination to be made as to whether or not the illumination angle in the lateral direction of the headlamp is within a proper range. More particularly, the invention relates to a leveling device for measuring an amount of lateral inclination of a vehicular headlamp so that the illumination angle of the headlamp can be properly adjusted in the lateral direction thereof when the angle is outside the proper range.
A description will herein be given of a headlamp of a movable-reflector type automobile headlamp by way of example, in which type a reflector is tiltably mounted in a lamp body. FIG. 1 shows an example of a headlamp this type. As shown in FIG. 1, a reflector 2 is supported at three points with respect to a lamp body 1, namely, by two aiming screws 3 and 4, and one fulcrum 5 of a ball joint structure. (The aiming screws 3 and 4 extend perpendicular to the plane of FIG. 1.) The aiming screws 3 and 4 are rotatably retained in the rear wall of the lamp body 1. The points at which the reflector 2 is supported by the aiming screws 3 and 4 are arranged, for example, at right angles with respect to the pivot fulcrum 5 as viewed from the front of the lamp. The aiming screws 3 and 4 are turned to cause the reflector to pivot about the horizontal axis Lx and the vertical axis Ly, respectively, in order to adjust the illumination angle of the headlamp. Reference numeral 6 denotes a bulb provided as a light source which is mounted on the reflector 2.
On the other hand, in the case of a movable-unit type headlamp (not shown), an integrally combined lamp body and reflector unit is pivotably mounted with respect to a lamp housing of the body of the vehicle. In this case, the reflector surface is integrally formed on the inner peripheral face of the lamp body. The unit is tiltably mounted by one pivot fulcrum and two aiming screws so as to be tiltable with respect to the housing, similar to the case of the movable-reflector type headlamp of FIG. 1. The aiming screws are turned to make the unit pivot in order to adjust the illumination angle of the headlamp.
In automobile headlamps such as those described above, the movable member (i.e., the reflector in the movable-reflector type headlamp or the unit in the movable-unit type headlamp) the illumination direction of the lamp is adjusted vertically (by pivotal movement about the horizontal axis Lx) and laterally (by pivotal movement about the vertical axis Ly) with respect to a reference member (i.e., the lamp body in the movable-reflector type headlamp and the housing in the movable-unit type headlamp) by turning the two aiming screws to adjust the irradiating angle of the lamp.
Recently, various leveling devices for measuring the illumination angle in the lateral direction of a lamp have been proposed. For example, co-assigned U.S. Pat. No. 5,067,056 discloses such a leveling device which includes, as shown in FIG. 2, a tubular fixed holder a fixedly fitted into a hole 1a formed in the back wall of a lamp body 1, a movable holder b screwed into the fixed holder a, a sliding rod c passing through the movable holder b in such a way that its leading end abuts against the back side of a reflector 2 while being urged thereagainst, and relative graduations d.sub.1 and d.sub.2 provided between an extension of the movable holder b at the rear of the lamp body. The lateral inclination of the reflector, that is, the lateral illumination angle of the headlamp, can be measured from the amount of misalignment between the graduations d.sub.1 and d.sub.2 between the holder b and the sliding rod c.
However, the holder b in the aforementioned leveling device projects rearward from the lamp body 1 a conspicuous amount as it is necessary for the assembly worker to read the graduations d.sub.1 and d.sub.2 by looking at the leveling device projecting from the back of the lamp body from a vantage point above the headlamp while the headlamp is mounted on the vehicle body. For this reason, sometimes an object may bump against the holder b and damage the leveling device when the headlamp incorporating the leveling device is mounted on the vehicle body. Although flanges e formed on the fixed holder a are fixed to the lamp body 1 with screws when the leveling device is fitted to the headlamp, the work of fixing the flanges takes time because the positioning of the fixed holder a in the peripheral direction is quite difficult.